European Union representative Miguel Arias Cañete speaks during a news conference in Quito, Ecuador. BRUSSELS—Days before negotiations for a global deal to fight climate change kick off in Paris, the European Union’s climate and energy czar warned that an agreement is far from certain. Next Monday, world leaders will open two weeks of talks in the French capital on how to protect the planet from the potentially catastrophic consequences of global warming. If successful, the Paris climate conference, also known as COP 21, could, for the first time, bind developed and developing countries into cutting greenhouse-gas emissions. But after four years of preparations, big gaps remain among the 195 governments that have to agree unanimously on any deal. At a summit of the Group of 20 industrialized and developing nations this month, some governments questioned central elements of the deal—including the overall target of keeping global temperatures from rising […]